Our choice to show up at weddings as a family unit wasn’t just a cute stunt. It was an extension of our political beliefs that friendship is a relationship that’s equal in importance to romantic and family bonds.

The historian Stephanie Coontz, who studies marriage and family structures in America and Western Europe, notes that, in the same way that societies have changed their definitions and expectations of family and romantic relationships over time, the expectations for friendship have evolved over centuries. (Until we called her, Coontz, who makes her living studying intimate relationships, had never been asked about how marriage and family structures affect friendships!) She gave us a brief history of how powerful people in Western society have set the standards for friendship, and how people of other class and racial groups often developed their own variations on those standards.

In the 16th and 17th centuries, marriages tended to be arranged to make political or economic alliances or to create community solidarities. “Love was nice if it came afterwards, but it was not considered a good reason for marriage,” Coontz says. “And so friendships were very different and perhaps more emotionally central to people.”

In the late 18th and 19th centuries, when it became common to marry for love, middle-class people began worrying that the couple would have no reason to stay married if their affections dissipated. With more men working outside the home, women were newly responsible for domestic life, and the idea of separate spheres developed. This was an early version of the notion that men are from Mars and women are from Venus, with different sets of inherent skills and social roles. All men were now supposed to be ambitious, hard-nosed, and interested in public matters. And women were supposed to be sexually pure, emotional, and nurturing. 

If men and women are two sides of a coin, the theory went, they must get married and stay married in order to access the supposedly innate traits of the other. You complete me. “So this led to this intense romanticization of the other,” Coontz says, “but also it opened the way for a real flowering of male/male and female/female friendships, because those were the people that you had everything in common with, supposedly.”

In letters to each other during the 19th century, some women refer to men as “the grosser sex.” Friendship, not romantic relationships, were a place where women felt free to be themselves and express their emotions. And intense female friendships, even those that might seem erotic to modern eyes, were accepted because women were supposedly so pure that they wouldn’t have sex with each other, even if they slept in the same bed all night. 

If a woman professed to have a crush on another woman, it wasn’t seen as commentary on her sexuality. “Men also had very intense friendships,” Coontz says. She points to letters in which men who identified as heterosexual “talk about falling to sleep with their head lying peacefully on the breast of their good friend.”

Toward the end of the 19th century, middle-class Americans began to recognize that these ideas made it hard for men and women to construct intimate marriages. Gradually, middle-class Americans adopted the practice of dating, which had already emerged in the working class. It became more acceptable for women to appear in public, even to work. This led to the rise of what was called “companionate marriage.” It was not yet the era of “I married my best friend,” but it became accepted that women and men should share activities—though emphasis was still placed on women adapting to men’s interests—and pursue a mutually fulfilling sex life.